Luigi obtaining King Boo's Crown.
King Boo's Crown is the final piece of jewelry Luigi collects before he saves Mario in Luigi's Mansion. In Luigi's Mansion, the crown holds a red diamond at the top. Officially, King Boo's crown also counts as a Red Diamond. The crown is worth the same amount as a single coin.
The crown has changed in the later Mario games it has appeared in. It is nowadays shown as a golden crown encrusted with jewels, similar to Princess Peach's crown.
In Luigi's Mansion: Dark Moon, however, King Boo appears to sport the crown's initial appearance, except the gem, which is different and gives him enough power to shatter the Dark Moon.
- King Boo's Crown is the only unit of money in the game that must be collected, so, albeit hard, it is possible to only get $5,000.